1. Field of the Invention
The present invention relates to an acoustic communication terminal apparatus for communicating with a communication partner over a telephone line by the use of an acoustic coupler, and relates also to a recording medium for storing a control program for such an acoustic communication terminal apparatus.
2. Description of the Prior Art
Conventionally, an acoustic communication terminal apparatus outputs a signal to be transmitted to a partner in the form of an acoustic signal. This acoustic signal is converted into an electric signal by an acoustic coupler, and is then transmitted to the partner over a telephone line. On the other hand, a signal received from the partner over the telephone line is converted into an electric signal by the acoustic coupler, and is then subjected to various kinds of signal processing.
Here, the acoustic communication terminal apparatus has an acoustic output circuit and an acoustic input circuit. As shown in FIG. 9A, in the acoustic output circuit, a signal 30 to be transmitted to a partner is modulated by a modulation circuit 31, is then amplified by an amplifier circuit 32, and is then output from a loudspeaker 33 as an acoustic signal. The acoustic signal thus output from the loudspeaker 33 is then converted into an electric signal by a microphone of an acoustic coupler, and is then transmitted to a partner over a telephone line.
On the other hand, as shown in FIG. 4B, in the acoustic input circuit, an electric signal received from the partner over the telephone line is converted into an electric signal by a microphone 34 of the acoustic coupler, is then subjected to noise elimination performed by an input filter circuit 35, is then amplified by an amplifier circuit 36, and is then demodulated by a demodulation circuit 37 into the signal in its original form.
Here, the gains of the above-mentioned amplifier circuits 32 and 36 and the filter characteristics of the above-mentioned filter 35 are usually either fixed or manually adjustable. This often makes it difficult to avoid communication errors associated with environmental conditions and the condition of the telephone line. Moreover, it is troublesome to adjust the gains and the filter characteristics manually as required.
To overcome these inconveniences, for example, Japanese Laid-Open Patent Application No. H4-83455 discloses an apparatus provided with a detecting means for detecting a transmission error on the basis of a signal received from a partner apparatus and an adjusting means for adjusting the output sound pressure level of a signal to be output on the basis of error-related data detected by the detecting means. Thus, this apparatus can establish communication by adjusting the output sound pressure level in accordance with the signal received from the partner apparatus.
However, this apparatus works on the assumption that it can receive a signal from a partner apparatus correctly, and therefore it cannot establish communication if it cannot receive a signal from a partner apparatus correctly. Moreover, whereas the output sound pressure level is adjustable, the operation performed to achieve reception remain the same throughout. This sometimes makes it impossible to continue communication when some change occurs in the signal being received due to a change in environmental conditions.
An object of the present invention is to provide an acoustic communication terminal apparatus that allows easy establishment and reliable continuation of communication, and to provide a recording medium for storing a control program for such an acoustic communication terminal apparatus.
To achieve the above object, according to one aspect of the present invention, an acoustic communication terminal apparatus is provided with: a transmitter for transmitting an acoustic signal; a receiver for receiving an acoustic signal; an error number counter for counting the number of errors occurring during communication; and a communication quality controller for improving the quality of communication by controlling the operation of the transmitter and the receiver according to the number of errors counted by the error number counter.
This acoustic communication terminal apparatus automatically counts the number of errors occurring during communication and controls the operation of both the transmitter and the receiver according to the number of errors thus counted. Accordingly, it is possible to remove the cause of an error irrespective of whether it is due to a fault in transmission or reception, and thus it is possible to establish and continue communication reliably. Moreover, it is possible to secure high quality of communication even when a change occurs in environmental conditions.
Here, what is controlled in practice is, for example, the amplifying operation performed by the transmitter and the receiver, or the filtering operation performed by the receiver.
According to another aspect of the present invention, a recording medium has a program stored thereon that is to be run on an acoustic communication terminal apparatus that achieves communication by acoustic coupling, and the program includes: a transmission step of transmitting an acoustic signal; a reception step of receiving an acoustic signal; and a step of improving the quality of communication by counting the number of errors occurring during communication and by varying the operation performed in the above-mentioned transmission and reception steps according to the number of errors counted.
By designing an acoustic communication terminal apparatus to operate according to the program stored on this medium, it is possible to establish and continue communication reliably, and to secure high quality of communication even when a change occurs in environmental conditions.